How Yahoo’s Image Caching Will Impact Your Email Marketing Metrics

Posted by Zach Sheehan on March 19, 2018

Return Path has noticed that Yahoo Mail is in the process of deploying image proxy servers which will have an impact on your open rates and the ability to glean additional engagement data. As you may recall, Gmail made a similar move in December 2013, so this isn’t exactly uncharted territory.

Image proxy caching stores copies of images on proxy servers for reuse. So the second time a user requests the images, or in this case opens an email to display images, the images are pulled from a stored local copy at the mailbox provider versus being downloaded from remote servers.

While there’s been no official communication from Yahoo regarding this change, Gmail deployed proxy servers for image proxy caching to improve downloads speeds and protect end users from malware.

Users of Return Path’s Email Client Monitor will experience the following changes in reporting after Yahoo fully rolls out this update:

Open ratesECM users will now see only unique open rates. Subsequent opens will pull image tracking from the cache and therefore won’t show multiple opens by any one person.

GeolocationThe geolocation data will only display Yahoo’s proxy servers, so most of your Yahoo opens will appear to occur in Mountain View, CA.

Device informationWhile we can still determine whether someone opened an email from Yahoo, the user agent string (which helps us determine the exact device type someone opened an email on) will no longer be passed along from Yahoo. Instead, all Yahoo opens will now appear in the Yahoo Mail category for webmail.

One exceptionThese changes should only impact mail opened in the Yahoo webmail interface or the Yahoo Mail app. Yahoo mail that is opened in other email clients—like iOS Mail, for example—won’t have these limitations.

With Yahoo webmail or Yahoo Mail app only accounting for one percent of all total opens as of February 2018, this change is unlikely to significantly impact most marketers. Comments? Concerns? Questions? Leave me a note in the comments.

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About Zach Sheehan

Zach Sheehan is an Associate Project Manager at Return Path. His goal is to create great products that help customers innovate their email programs. In his free time, Zach enjoys watching football and basketball with his dog Milo Connect with Zach on LinkedIn.